Edwards syndrome

Background

Edwards syndrome is a chromosome abnormality where the child has
an extra chromosome 18 in every cell. It is a rare disorder, seen
in about 1 in 4,400 live births.

There are three types of the syndrome:

Full form - in this form, every cell in the body has three
chromosome 18s instead of two (94 per cent of cases).

Mosaic form - in this form, some cells have two chromosome 18s
while others have three. The extent and severity of the condition
will depend upon the ratio of normal to abnormal cells.

Partial form - in some cases there may be an extra copy of part
of chromosome 18. This is referred to as 'partial trisomy 18'. The
effects of this may be milder and would require further specialist
advice.

Children with the full form do not often survive beyond infancy,
with about 10 in 100 (10%) expected to live past one year of age.
Those affected by the mosaic and partial forms may sometimes
survive into adulthood.

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preparation of all entries to ensure accuracy, we cannot accept
responsibility for any errors or omissions. Any medical information
is provided is for education/information purposes and is not
designed to replace medical advice by a qualified medical
professional.

How is it diagnosed?

Edwards syndrome is often detected during pregnancy (see
prenatal diagnosis) and some parents opt not to continue the
pregnancy. In about 30 per cent of cases (higher for affected males
than females), a spontaneous miscarriage occurs.

Sometimes a baby may be born with features of Edwards syndrome
after normal scans in the pregnancy. In this situation, a blood
sample from the baby will be sent for karyotype analysis to confirm
the diagnosis.

How is it treated?

Parents should meet with the obstetric and neonatal teams to
discuss the diagnosis and to prepare for delivery and the care of
their baby. It is likely that the baby will be admitted to the
special care baby unit, and will require supportive treatments over
the first days of life.

Many babies with Edwards syndrome have a structural heart
problem (see entry Heart Defects). Babies are likely to
require long-term nasogastric tube feeding, and may be more
comfortable if they are given medicine to prevent
gastro-oesophageal reflux. In addition, these babies may also need
help with breathing.

Sadly, about half of babies born with Edwards syndrome do not
survive longer than one week, with about 10 in 100 expected to live
past one year of age. If a baby is well enough to leave hospital,
community support arrangements should be put in place, and
follow-up plans made with the local paediatric team.

Inheritance patterns and prenatal diagnosis

Inheritance patterns
Edwards syndrome usually occurs as a "one-off" (sporadic), and
therefore it is extremely unlikely that parents will have more than
one pregnancy affected by Edwards syndrome. In rare cases, a
balanced translocation in a parent can give rise to an unbalanced
translocation in their child leading to a higher risk in the next
pregnancy. This situation is detected on the baby's karotype.

Prenatal diagnosis
Women are offered a combined blood test and scan between 12 to 14
weeks into a pregnancy to screen for Down's syndrome. These tests
have recently been changed to report a risk for Edwards syndrome.
If a high risk is detected a chorionic villous sample or
amniocentesis is offered which can diagnose Edwards syndrome.

Routine ultrasound scanning at 18 to 20 weeks can detect
physical features of Edwards syndrome in over 70 per cent of cases.
If an ultrasound scan suggests a high risk of a chromosome problem,
a definitive genetic test to look at the baby's chromosomes will be
discussed.

Is there support?

SOFT UK

The Organisation is a Registered Charity in England and Wales
No. 1002918. It provides information and support for families
affected by Trisomy 13 (Patau's Syndrome), Trisomy 18 (Edwards'
Syndrome) and related disorders, including prenatal information and
bereavement support.